OT: Is This RF Or Power?

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On Tue, 20 Jan 2004 15:00:06 GMT, "Randy Chapman"

For CAD/graphics work? I'd rather be buried alive in an ant hill. (But that just might solve the RF problem.)
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brought forth from the murky depths:

Gentleman may differ. I bought 2 syncmaster 213Ts just to do CAD/graphics...
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Whoa Larry. Just picked up a 19" ViewSonic to replace a 19" (really 18") CRT that just died a week ago. I've had dual monitors hooked up for several years now and when I stretch a CAD drawing across both screens, the LCD is much easier to look at in comparison.
Maybe your experience was with an older model / technology. The model I have isn't top of the line (double the cost too) but sure is better than my analog CRT's.
Bob S.
brought forth from the murky depths:

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As others have said, it's hard to tell for sure, but my vote is for a magnetic field problem induced by the large current from the welder. I had a user once whose monitor was giving a "wavy" display. I went into the cube on the other side of the wall from her monitor and found a small desk fan. I turned the fan off and presto, no more interference. If a little fan like that can create enough of a magnetif field to cause her monitor problems, you can imagine what a welder would do. But I've got good news. I just saved a load of money by switching to GEICO. Also, magnetic fields dissipate by the inverse square of the distance from the source, so if you can move your monitor far enough away from the wall, you might eliminate the problem. The bad news of magnetic fields is that they're famously difficult to shield. As an alternative, you could switch to an LCD as another poster pointed out.
todd
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GSM cell-phone next to the monitor by any chance ?
Ray
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Look for something with the 2 minute cycle. A high intensity dicharge lamp( mecury vapor) has both the current draw and electronics to cause this type of problem. If the bulb or the electronics is bad you will have a startup cycle problem, that if I remember takes about two minutes to cycle thru. Some electronic ballast flourecents may cause a problem but there is not the current draw to cause a large RF burst.
Tom Watson wrote:

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Crt's can be very much affected by power.
(A) Large power panels will drive certain models nuts. (B) The welder will almost certainly create short bursts that will make the monitor "jump".
You can two different things:
(a) Shield the wall (b) Move away from any large power panel.
The strips will have little effect on the monitor.
Certain monitors are better protected than others. Try a different monitor at the same location.
Tom Watson wrote:

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Tom,
As an aid to diagnosing the problem try rotating the monitor in the horizontal plane for a while. The disturbance you are seeing, if caused by a magnetic field is going to be a function of the orientation of the CRT. Consequently it should change markedly if you rotate the monitor 90 degrees. If it doesn't change then its a good guess it isn't magnetic in origin.
RB
Tom Watson wrote:

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brought forth from the murky depths:

RF. All of the new MIG welders have an RF circuit for managing the arc.

Either call Lincoln and/or Hobart to see if they have any suggestions or get your neighboring welding shop to do so. Giving them the model number will help. They would be more likely to know what is causing it and how to fix it.

Possibly. But covering your offices in a Faraday cage would be better. ;) http://www.physics.gla.ac.uk/~kskeldon/PubSci/exhibits/E3 /

Graphics programs are like that, too. I had a girlfriend dust my office once, and for 2 days I couldn't figure out what had caused the jittery monitor problem. I finally figured out that she had set the electric clock on the shelf above the monitor and the 60hz motor magnetics were dropping down almost a foot to wreak visual havoc upon said monitor.
BTW, it was great talking to you on the phone last night. I had wondered where you had disappeared to. I seldom include an accent in my visualization of Wreckers so yours surprised me a bit. You appear to be a book fan, reading as much or more than I do. (I keyed on that more from your posts than from our discussion.)
P.S: Until it's resolved, taking a break from the spreadsheets is a great way to pass the time while they weld.
P.P.S: Go over there yourself. Get to know them. Welders are very handy pals to have around. ;)
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Larry Jaques wrote:

Oooh, oooh, what kind of accent does Tom have?
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On Tue, 20 Jan 2004 17:38:18 -0500, Silvan

GnuYawkish/PennsylTuckyish, I reckon.
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Ahem - Senior Computer Dork, if you please...

Get a hobby? You ever considered wooddorking? [ There are two 'D's, aren't there? ]
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Another possibility is "none of the above". <grin>
The most likely culprit _is_ power. A momentary 'sag' when some big piece of equipment is turned on, "somewhere in the vicinity.
Second possibility is that the welder -- *IF* it is electric arc (of some form) and used intermittently -- is throwing a large _magnetic_ field when energized, and that this is fouling the screen. If the piece of equipment happens to be an electric "spot welder", it could create the described effects.

FIRST THING is to identify the causative factor(s). See if there's a different circuit available, that you can plug the computer into. Try moving to different location in the room, etc.
Assuming it's a 'power' problem, you need a 'line stabilizer', AKA 'line conditioner'. A typical "Un-interruptible Power supply" will _not_ help with this issue -- they are a 'stand-by' device that cuts in -only- when the power fails completely.
If it _is_ a magnetic field problem, then the effective cure is _move_ the affected stuff further away from the source.

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On Tue, 20 Jan 2004 23:17:53 +0000, snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) brought forth from the murky depths:

Umm, a 2-minute long "momentary sag", Robert? Besides, computers operate on +-5v and 12v power. Their power supplies can handle pretty big sags and filthy power before turning off or acting up.

Right, constant voltage supply. I left one in CA when I moved. Too damned heavy!

What, no tinfoil hat for the monitor? <g>
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"Reading counts", Larry. With extra points for reading comprehension. The _facts_:
1) He didn't say it _lasts_ two minutes, he said it *occurs* every two minutes or so. The =duration=, according to the original poster is about *one*second*. That _is_ accurately characterized as a 'momentary sag'.
2) The problem is with the *monitor*, not the computer. The high-voltage 'drive' sections of the CRT are step-up transformer, and voltage- multiplier section, -driven; from the power line, There _may_ be a 5V supply for some of the solid-state components. (some units I've seen and/or worked on had solid-state components that ran off voltage in the circa 50V range.) There almost assuredly is -not- a 12V supply _in_the_monitor_. 12V is used in computers for (a) RS-232 serial-port driver chips, and (b) motors of assorted sorts, primarily disk-drives of various types, but also some fans.
3) I'll agree "dirty power" is usually -not- a problem. For CRT's, however, 'sags' *are* an issue. For *safety* reasons, there is usually very little 'carrying time' in the HV sections. You _want_ the HV to die *quickly* if/when the mains power is removed.

Not necessarily a true CV supply. Those are *really* nice, but *heavy*, and _expensive_. Tripp, and some other people make units with multiple-tap buck/boost transformers coupled with voltage-sensitive relay switching. They're relatively fast acting (i.e., within a power cycle or two.) and cut in/out some fixed stages of buck/boost to 'normalize' the output voltage. _Much_ less expensive than a CV transformer of similar AMPacity, e.g. an 1800 watt 'stabilizer' is less than US$100, new. And weighs in at less than 5 lbs. A _clear_ 'winner', when you can tolerate 'limited' fluctuations in the mains power. I've got a unit that will hold the output voltage to within the range of 115-125V, for input voltages ranging from 85V to 145V. Doesn't help _at_all_ if the power fails completely, but eliminates any of the other 'surprises'.

Nope. Too much heat being generated. Good way to 'cook' the electronics inside. Tinfoil is of very limited effectiveness against magnetic pulse anyway -- more effective against RFI. Magnetic pulse strength is inversely proportional to "between distance squared, and distance cubed". Moving further away is -much- simpler/cheaper/more-effective than trying to construct something to block/attenuate the pulse.
However, I =did= solve an _RFI_ problem in an office that way once. Completely wrapped the affected piece of machinery in Renoylds Wrap (heavy duty, _wide_), and ran a wire to the center screw on the duplex outlet that it was plugged into. People in the office thought I was *crazy*... until the fix _worked_, that is. :)
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On Wed, 21 Jan 2004 07:18:14 +0000, snipped-for-privacy@host122.r-bonomi.com (Robert Bonomi) brought forth from the murky depths:

around that of your average Shrub supporter. Sorry.

This was one from a hospital. CV/Iso, the whole bit. About 200 lbs.

Speaking of reading comprehension, what's that <g> behind my silly suggestion?

Pulling crazy stunts is great fun, wot?
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Sounds like it was made by SOLA, and rated for about 300 watts. Nah, at 200 lbs, more like 450 watts. The 300 watt unit is only about 140 lbs. makes one h*ll of a door-stop and/or toe-stubber when not hooked up. <grin>

A self-assigned letter grade, one level _worse_ than an <f>, maybe? *snicker*
BTW, I've _seen_ people do *exactly* that. With results ranging from 'merely' frying the monitor, to tripping the overhead water.
Sometimes one has to treat the frivolous question seriously, to prevent the "*doesn't* know any better" third party from implementing it.

I learned a few things from a _real_ master. He was chief engineer for one of the big network TV stations in town, and volunteered for theater dept support at the H.S. I attended. One day, there was a problem with an audio feed -- he grabs two _shielded_ audio cables. lines 'em up together for about 3 feet, ties a big overhand knot with the paired cables, and throws it on the wooden stage floor. *Without* plugging the connectors on the cables together. The truly scary thing is _IT_WORKED_! To this day, I don't understand the 'how' or 'why' of it. Even though I, a few months later, did exactly the same thing, to deal with the same problem at the same place. And it worked for me, too.
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Comprehension level of a Shrub critic.

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It could be either EMI or a power surge. I'm thinking EMI because of the welding equipment. If you have and UPS unit or know of a friend who has an UPS (uninterruptible power supply) w/ a surge suppressor the unit should still supply power without interruption during a power spike or drain. EMI is a much more complex problem. requires a lot of bonding, shielding, and the like Been dealing with it for years on ships and I'm still not sure how the theory works on all the measures we take to reduce it. I do know that if we key up a handheld radio in a room w/ a computer in it that the screen will jump. Occasionally the screens on monitors and TV's will have a green hue to them and we have to degauss them because of the effects of EMI (electromagnetic interference). So this could be another indicator (a soldering gun can sometimes act as a degausser). Anyway my first course of action would be to run my computer off and UPS without it plugged into the outlet and see if the screen jumps when someone fires up the welder. With the computer running off battery power you should not see the effects of a power spike/drain with the welder in use. If the problem does occur then your dealing with EMI and the solution will most likely be more troublesome (and expensive) than the problem.
Joey in Chesapeake

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<Interesting monitor problem story snipped>
There are so many possibilities for this it is not possible to answer. Rick, in a previos post in this thread gave some good troubleshooting advice. I'll just add my $0.02 worth...
Unless the welder or whatever industrial device is cycling at two minute intervals, just ignore it. If it is cycling every two minutes, like in some production line, see below regarding power supplies. However, other equipment would probably show some signs if this were happening. If there were that much EMI there sould be significant health effects around the building by now, (and a great law suit). So let's ignore that for now.
The most likely culprits are the computer and the monitor.
1) The computer. a) Is there a CD/DVD sitting close to the monitor? Is your CD/DVD or similar being accessed every two minutes? Perhaps for license verification or graphics/clip art/music refresh? (App controlled) b) Power supply issues. b1) Power supply not operating properly. b2) Input line voltage dropping below reliable operating range of the power supply. This could effect other systems in your PC but the more obvious impact could be on the video display adaptor. Some of these can become tempramental when their operating tolerances are not met. ## One possible cause could be momentary spikes from the welder, depending on how/where the branch curcuit was installed. Other 2) The Monitor. a) Bad tube or internal controller. System componets often fail in a cyclic manner before fully quitting. (i.e. It could be a degaus curcuit is firing due to a failing contoller. b) Line voltage dropping below reliable operating range of the power supply. ## One possible cause could be momentary spikes from the welder, depending on how/where the branch curcuit was installed.
I think that more than my two cents worth, and its worth every cent!
Good Luck, Myx
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